Hospital infections kill more Americans each year than AIDS, car accidents and breast cancer combined — and researchers are searching for solutions. This week, a study of 153 Veterans Affairs hospitals shows that doing a simple swab test to identify and isolate the few patients carrying infection-causing bacteria can save lives. It’s called screening, but even more important is cleaning. Studies are rolling in that hospitals need to be cleaner.

In fact, if you’re visiting a friend or relative in the hospital, don’t bring flowers or candy — take gloves and a canister of bleach wipes.

Hospitals do an inadequate job of cleaning rooms — so germs left behind by past patients are lying in wait. Patients are at far greater danger of infection when placed in a hospital room where a previous patient had an infection. Hospitals won’t tell you who occupied the room before you.

Alarming research published in the Archives of Internal Medicine (March 28) demonstrates that a patient’s risk of picking up the drug-resistant bug MRSA (methicillin-resistant Staphylococcus aureus) is much higher if the previous occupant of the hospital room had it.

Being placed in a room where the last patient had Clostridium difficile, or C. diff for short, more than doubles the risk of getting that dreaded infection, according to a new study in Infection Control and Hospital Epidemiology (March 2011). C. diff is the most common hospital infection in some parts of America.

Patients pick up invisible C. diff bacteria when they touch surfaces in their room, then eat a roll or cookie with their contaminated hands and swallow the bacteria along with the food.

C. diff causes life-threatening diarrhea — wreaking havoc in your gastrointestinal system unless you have enough powerful “good” bacteria in your system to keep the C. diff under control. But patients on antibiotics often lack good bacteria. Some hospitals are treating desperately ill patients by giving them fecal enemas.

Pretty awful. Especially when it could be avoided by keeping the patient’s room clean.

Dr. Robert Orenstein launched a cleanup campaign at the Mayo Clinic in Rochester, Minn. — wiping the frequently touched surfaces around each patient’s bed once a day with bleach-soaked wipes. The results: a 75 percent drop in C. diff infections.

Lax room-cleaning raises the risk of contracting other kinds of hospital infections, too. The No. 1 predictor of which patient picks up a drug-resistant bug called VRE (vancomycin-resistant Enterococcus) is who occupied the patient’s room in the prior two weeks, according to Tufts University investigators. That two-week span could mean three or four patients ago.

A study of 36 hospitals from Boston to Washington, DC, found that cleaners routinely overlook half the surfaces in patients’ rooms. Toilet seats are cleaner than telephones and call buttons.

Doctors and nurses may clean their hands coming into the room — but recontaminate them when they open the privacy curtain or rest their hands on the bedrail. Then they touch their patient, and germs enter the patient’s body via an IV, urinary-tract catheter, wound or surgical incision.

For decades, hospital administrators and government agencies have shrugged off the notion that hospitals are dirty, saying, “germs are everywhere.” They emphasize getting doctors and nurses to clean their hands — which isn’t enough.

The Joint Commission, which is responsible for accrediting most hospitals, just considers whether a hospital looks clean — when infection-causing germs are invisible.

Food-processing plants routinely test surfaces for bacteria. Hospitals ought to meet at least the same standard.

Betsy McCaughey is founder of the Committee to Reduce Infection Deaths, a New York-based non profit.